U.S. Pat. No. 4,508,842 discloses a highly active vanadium-containing catalyst capable of producing ethylene polymers having a broad molecular weight distribution. Said catalyst comprises:
(A) a solid catalyst component
consisting essentially of
(1) an inorganic carrier, as support for PA1 (2) the reaction product of (a) a vanadium trihalide and (b) an electron donor, and PA1 (3) a boron halide or alkyl-aluminum modifier, PA1 (1) a solid catalyst component obtained by precipitating vanadium trihalide from an ether solution onto a silica and/or alumina carrier and then treating the product with an alkylaluminum, PA1 (2) an alkylaluminum, PA1 (3) an alkyl halide, and PA1 (4) an alkoxy compound of silicon. PA1 (1) a solid, particulate, porous inorganic carrier, as support for PA1 (2) the reaction product of (a) a vanadium trihalide and (b) an electron donor, and PA1 (3) a boron halide or alkylaluminum modifier, PA1 n is a number having a value of from 2 to 100, PA1 R.sup.1 is hydrogen or a monovalent hydrocarbon radical free of aliphatic unsaturation containing from 1 to 20 carbon atoms, PA1 R.sup.2 is a monovalent hydrocarbon radical free of aliphatic unsaturation containing from 1 to 20 carbon atoms, and PA1 R.sup.3 is selected from the group consisting of: --X, --R.sup.1, --OR.sup.1, --COOR.sup.1, and --NR.sup.1 R.sup.2 PA1 X is halogen and R.sup.1 and R.sup.2 are as defined above. PA1 (1) a solid, particulate, porous inorganic carrier, as support for PA1 (2) the reaction product of (a) a vanadium trihalide and (b) an electron donor, PA1 (3) a boron halide or alkyl-aluminum modifier, and PA1 (4) a polysiloxane oil activity regulator having the formula: ##STR2## wherein: R.sup.1, R.sup.2, R.sup.3, m and n are as defined above, PA1 (1) a solid, particulate, porous inorganic carrier, as support for PA1 (2) the reaction product of (a) a vanadium trihalide and (b) an electron donor, PA1 (3) a boron halide or alkylaluminum modifier, and PA1 (4) a polysiloxane oil activity regulator having the formula: ##STR3## wherein: R.sup.1, R.sup.2, R.sup.3, m and n are as defined above. PA1 M is boron or AlR.sup.4.sub.(3-a) wherein each R.sup.4 is an alkyl radical containing from 1 to 14 carbon atoms, which radicals may be the same or different, PA1 X is selected from the group consisting of fluorine, chlorine, bromine and iodine, and mixtures thereof, and PA1 a is an integer having a value of 0, 1 or 2, provided that a is 3 when M is boron. PA1 n is a number having a value of from 2 to 100, preferably from 3 to 10, PA1 R.sup.1 is hydrogen or a monovalent hydrocarbon radical free of aliphatic unsaturation containing from 1 to 20 carbon atoms, PA1 R.sup.2 is a monovalent hydrocarbon radical free of aliphatic unsaturation containing from 1 to 20 carbon atoms, and PA1 R.sup.3 is selected from the group consisting of: --X, --R.sup.1, --OR.sup.1, --COOR.sup.1, and --NR.sup.1 R.sup.2 PA1 X is halogen and R.sup.1 and R.sup.2 are as defined above. PA1 R.sup.2, is usually an alkyl radical containing from 1 to 20 carbon atoms, preferably from to 1 to 6 carbon atoms, or an aryl radical containing from 6 to 20 carbon atoms, preferably 6 carbon atoms. R.sup.1 is usually hydrogen or a like alkyl or aryl radical, and R.sup.3 is usually halogen or a like alkyl or aryl radical. Such radicals may be substituted with one or more substituents which are inert under the reaction conditions employed during treatment of and polymerization with catalyst component (A). Typical substituents include chlorine and fluorine. PA1 (1) the reaction product of (a) a vanadium trihalide and (b) an electron donor, PA1 (2) a boron halide or alkylaluminum modifier, and PA1 (3) a polysiloxane oil having the formula: ##STR5## wherein: R.sup.1, R.sup.2, R.sup.3, m and n are as defined above. PA1 R.sup.6 is hydrogen or an unsubstituted or halosubstituted alkyl radical containing from 1 to 6 carbon atoms, which radicals may be the same or different, PA1 X' is halogen, and PA1 b is 0, 1 or 2.
(B) an alkylaluminum cocatalyst, and
(C) a halohydrocarbon polymerization promoter.
The polymers produced in accordance with U.S. Pat. No. 4,508,842 have a relatively broad molecular weight distribution, and excellent extrudability. These properties render them extremely useful in a wide variety of applications, such as wire and cable insulation, blow molding, film, and pipe fabrication.
Copending application Ser. No. 292,268 (now U.S. Pat. No. 4,000,327) of Sun-Chueh Kao et al. discloses that the activity of the catalyst disclosed in U.S. Pat. No. 4,508,842, supra, can be enhanced by treating the solid component thereof with an alkoxysilicon compound. However, such treatment also causes a narrowing of the molecular weight distribution of the polymers produced with such catalyst.
Japanese Public Disclosure No. 62-25112 (Application Ser. No. 60-163525) likewise discloses vanadium-containing catalyst compositions useful in the preparation of ethylene polymers having a narrow molecular weight distribution. Such compositions consist of:
Japanese Public Disclosure No. 56-22308 (Application Ser. No. 54-981281) is yet another reference which discloses vanadium-containing catalyst compositions useful in the preparation of ethylene copolymers having a narrow molecular weight distribution. The catalyst compositions of this reference are prepared by combining an organoaluminum compound and a solvent-soluble vanadium compound in the presence of olefin monomer and then adding polysiloxane to the mixture.